1. Field of the Invention
The present invention relates to a lens driving device, and more particularly, to a lens driving device capable of stabilizing and improving resonances and a method of manufacturing the same.
2. Description of the Prior Art
Those skilled in the art have endeavored to reduce or eliminate the negative impact on photos caused due to the shaking of the camera by the camera operator (the so-called hand shaking) during the photo taking session.
It is commonly agreed that the fast developing optical anti-vibration technique will become the mainstream anti-vibration technique in the future because this technique can prevent drawbacks such as poor image quality as a result of the correction made with software and longer latency of software processing.
In the field of optical anti-vibration, the significant “lens displacement based” optical anti-vibration method has advanced and developed rapidly in recent years. For example, the “common magnet” technique developed in recent years is advantageous in providing an optical anti-vibration function and minimizing the size of the lens driving device. The “common magnet” technique involves employing the same set of magnets to drive two sets of coils so that the lens can move in directions respectively perpendicular and parallel to the optical axis, thereby achieving the auto focusing and anti-vibration functions.
FIG. 1 is a schematic view showing the main structure of a conventional lens displacement based optical anti-vibration device. As shown in FIG. 1, magnets 6 and a coil plate 9 are disposed around a coil 3 and a lens (not shown). The interaction of the magnets 6 and the coil 3 causes the lens to move in an optical axis direction to perform the auto focusing function, and the interaction of the magnets 6 and the coil plate 9 causes the lens to move in a direction perpendicular to the optical axis to perform the optical anti-vibration function. Moreover, the conventional technique shown in FIG. 1 further comprises a displacement sensing device 12 (i.e. a Hall element) mounted on one side of the coil plate 9. No coil is arranged between the displacement sensing device 12 and the magnets 6 so that the displacement sensing device 12 can sense the displacement of the magnets 6 accurately.
According to the structure of the aforementioned conventional device, a coil 92 and a corresponding coil 94 of the coil plate 9 are asymmetric in length, and such asymmetry results in asymmetric forces that cause the occurrence of a yawing resonance in the lens driving device. The yawing resonance generates a force that causes the magnets 6 and the lens to rotate undesirably. For example, the magnets 6 and the lens, which are supposed to rotate solely in the X direction, also move in the Y direction (and vice versa), thus the displacement sensing device 12 will erroneously detect the displacement amount that is not supposed to exist and make an incorrect judgment.
In another aspect, according to the structure of the aforementioned conventional device, the peak of the first-order resonance of the coil plate 9, the magnets 6 and the lens will be significant and cannot be controlled easily, thereby negatively affecting the anti-vibration effect and image quality.